Colostrum feeding at lung consolidation diagnosis enhances growth around weaning without ameliorating disease severity in dairy calves

Lung consolidation affects calf welfare and their future productivity in the lactating herd. Moreover, judicious antimicrobial use in dairy cattle management requires searching for nutraceutical alternatives. Colostrum is an opportunity as it has immune-mediating properties such as immunoglobulins, probiotics, lactoferrin, and bioactive compounds. This randomized controlled trial evaluated the association of a single colostrum replacer (CR) feeding, compared with a milk replacer (MR), with growth in Holstein calves with lung consolidation (LC); it was also evaluated whether CR feeding improved the likelihood of LC resolution within 10 days. A randomized block design balanced by sex was used to assign calves to their study treatment. Calves with naturally occurring LC (≥ 1cm 2 , n = 55; MR = 28; CR = 27) were enrolled upon the first detection of LC from 3 to 7 weeks of life. At LC diagnosis calves received one bottle feeding of CR (4.84 ME/kg, Premolac Plus, Zinpro; 250 g/2 L water; 114 g IgG; CP = 70%; Fat = 8%), or MR (4.85 ME/kg, HerdFirst, Cargill; 250 g/2 L water; CP = 26%; Fat = 20%). From birth to 7 weeks of age, calves were fed 7.5 L/d of MR by bottle split into two daily feedings. On day 50, calves were fed milk once daily until complete weaning at 8 weeks. Thoracic ultrasound examinations were performed 3 x/week from 3 to 9 weeks until study completion (64 ± 2 days). Calves were weighed at birth, weekly, and at study completion. A linear regression model was used to evaluate the association of CR feeding with calf average daily gain (ADG) for the 7 days following intervention (short-term), adjusting for body weight at enrollment. A mixed linear regression model was also used to evaluate the effect of CR on ADG during weaning (8 weeks) and post-weaning (9 weeks), adjusting for the fixed effects of week, birthweight, CR, and testing the CR × week interaction. The model had week as a repeated measure, and calf nested within block as a random effect. A Cox proportional hazards model was also used to evaluate the likelihood of CR feeding resolving LC within four examinations following diagnosis (e.g., within 10 days), adjusting for block as a random effect. The average age at LC onset was 33 ± 9 days. Short-term ADG was not associated with CR feeding ( p = 0.53). There was no CR × week interaction for calf ADG, but CR calves had greater ADG than MR calves for the weaning and post-weaning period (CR 1.04 ± 0.06 kg/d, vs. MR 0.85 ± 0.06 kg/d; p = 0.03). There was no association of CR feeding with the likelihood of resolving LC within 10 days (hazard ratio 1.17; 95% CI: 0.54 to 2.49; p = 0.69). These results suggest that one feeding of CR (114 g IgG) at the onset of LC improved ADG surrounding weaning but did not ameliorate disease. We suggest that future studies should elucidate which CR mechanisms enhance calf performance surrounding weaning.